1. Field of the Invention
The present invention relates to radar systems and methods, and more particularly to a method employing radar to locate a magnetically excited object.
2. Description of Related Art
Electronic detection of metal objects, particularly hidden metal objects, traditionally involves a “metal detector” that includes an electromagnetic loop coupled to an oscillator and detector. When the loop is placed near a metal object, its inductance changes and produces a change in the oscillator's frequency, which is detected. Modern versions of this technique employ pulse methods. In either case, detection range is sharply limited by a third power decrease in magnetic field strength versus range to the target. Since the magnetic field must travel out to the object and then couple back to the loop, a sixth order decrease in signal strength versus range results, forming a formidable limitation to long range operation.
Historically, radar has been used to sense mechanically excited motion or vibration in objects, such as rotating aircraft turbine blades. U.S. Pat. No. 6,492,933, entitled “SSB Pulse Doppler Sensor And Active Reflector System,” to McEwan, patented Dec. 10, 2002, describes a radar sensor that senses mechanically induced vibrations, wherein the mechanical vibrations may be the result of mechanical, acoustic, magnetic, optical, or electromagnetic excitation.
Background information on a radar motion sensor utilizing ultra-wideband radar is contained in U.S. Pat. No. 5,361,070, entitled “Ultra-Wideband Radar Motion sensor,” to McEwan, patented Nov. 1, 1994, including the following: “[u]ltra-wideband (UWB) radar motion sensing is a completely new approach to motion sensor technology. UWB radar operates as a pulse-echo system that docks the two-way time of flight of a very short electrical pulse. A carrier frequency is not used; instead, an electrical voltage pulse is applied directly to the antenna.”
Background information on a radar means for monitoring and imaging the movement of intra-body organs, tissues, and other structures and foreign objects embedded in a human or animal body is contained in U.S. Pat. No. 5,573,012, entitled “Body Monitoring And Imaging Apparatus And Method,” to McEwan, patented Nov. 12, 1996, including the following: “the invention is based on the pulse-echo radar principle of docking the two-way time of flight of an electromagnetic pulse. As used herein, the term radar impulse refers to a short radiated pulse, which replaces the long sinusoidal burst used in conventional radar technology. There is no specific frequency associated with impulse radar; rather, its frequency spectrum is related by the Fourier transform of the pulse.”
None of the prior art radar systems disclose a radar system tuned for optimal sensitivity of magnetically excited metal objects. Accordingly, a need exists for an accurate and sensitive method and system for radar detection of magnetically excited materials that includes ferrous and nonferrous materials. This new method and system is relatively inexpensive, easy to use by non-professional operators and is capable of being implemented in a variety of commercial and non-commercial applications.